Study of microbial diversity in saliva and plaque samples from caries-free and caries-affected children using denaturing gradient gel electrophoresis.

BACKGROUND: Recent investigations have shown the possible involvement of bacteria other than mutans group and Lactobacilli in the etiology of caries. Molecular methods have been used to study the microbial diversity in caries-active (CA) and caries-free (CF) children. Among them, denaturing gradient gel electrophoresis (DGGE) is more popular and has been used in the present study. AIMS: The aim of the present study was to investigate the difference in bacterial diversity in saliva and plaque samples from CF and CA children using DGGE. MATERIALS AND METHODS: The study involved saliva and plaque samples from 56 children of which 28 were CF, 20 with CA, and 8 with white spot lesions (WSP). DNA was extracted and subjected to polymerase chain reaction amplification with universal primers. It was then run in polyacrylamide gel electrophoresis with gradients of urea and formamide and stained with SYBR green. Multiple bands were produced in each sample lane and each band represents one organism. STATISTICAL ANALYSIS: A dendrogram was generated using Phoretix software and similarity index was calculated using a specific formula. RESULTS: Samples in each group formed several clusters indicating a specific pattern of the bacterial profile. Similarity coefficient was calculated based on the number of bands, intensity, and location. The diversity was less in the saliva and plaque samples of CA group as compared to those of CF and WSP groups. CONCLUSIONS: DGGE can be used to study distinctive bacterial profiles in healthy and caries-affected sites. DGGE can be further developed as a pattern recognition tool with which to identify specific groups of bacteria. Saliva may be used to study bacterial diversity in dental caries.